When a demon crosses worlds
by Razorreads2890
Summary: What happens when a demon crosses worlds for the second time? Self-insert story- M (Swearing)
1. Introduction

Welcome! This will be my first ever FanFic, so don't expect much of me. This will be an introduction chapter, meaning I'll tell you anything you need to know that will not be told in the next chapter.

First, this is a self-insert (somewhat) if this hasn't been told in the description (my apologies), then now you know. It will be a sort of weird self-insert, I'm throwing myself into a world, from another world besides our own. Yes, this will mean I will be throwing myself from Re:zero to Darling in the FranxX. I thought it was stupid at first but now, not so much.

Now, without further adieu welcome to my world.


	2. A change in scenery

Chapter 1 – Change in Scenery

It was a crisp summer evening in Lugunica, flowers were blooming, wind was blowing, and most of all the clattering of swords during training was ringing through the sky. Two people were sparring in the middle of an open field in front of a grand mansion. As the two sparred (one clearly more powerful than the other), three others were watching with great enthusiasm. They were rooting for the underdog, who was seemingly slowly getting the upper hand. Within the small crowd of three were: Roswall L. Mathers, Ram, and of course Rem. Roswall was there simply for entertainment and to oversee the sparring session, Ram showed up to see the underdog get beaten into a pulp, Rem came to see her hero do his best in the spar. The two sparring were Subaru, the knight in shining armor who always got the girl. Subaru was so adamant on training because he wanted to become Emilia's knight as soon as possible, despite the fact that he still had to do plenty of official training, and I the one that never got the girl despite being a far superior fighter in almost all regards.

The sparring session took almost two hours. Near the end I got bored and let my guard down for a split second, (purposefully) letting Subaru hit me with a left hook and quick swing of the sword. "You're doing much better than last time," Rem ecstatically started the conversation with.

"Well, I guess I am doing better," Subaru replied with a slight blush at Rem's happiness.

"Cause I let you win when I let my guard down," I cut in, making sure they know why he had won. If I hadn't let my guard down I could've kept fighting for days, at Subaru's pace.

"Either way impressive, both of you," Roswall had silently moved from his spot to behind me, weirdly quietly. Even Ram was uncharacteristically quiet, _"Something's going on that I'm not aware about,"_ I thought. My vision then went pitch black, there was a voice, a sort of soft whisper. It came from a women somewhere behind me, I couldn't move at all. _"What the hell's happening!"_ I screamed into the darkness. I was stunned that the words came out of my mouth, I had only thought of them. A familiar figure appeared, the jealous witch, or Satella. I had seen her before, every time Subaru tried to reveal that we could return by death I saw her. It was clear to me relatively quickly that Subaru doesn't see her like I do. _"What do you want with me!"_ I said, a little bit more calmly. I know that she can't harm me without hurting Subaru at the same time, I hope. "You were accidentally taken here," Satella continued, "I will leave you in another world at midnight tonight, much the same way I did when I brought you here."

" _So you're just going to drop me in another world?!"_ I filled with anger, every word in my sentence getting more aggressive as my sentence continued.

"Yes, you have until midnight," Satella whispered into my ear as I came to my senses.

* * *

I awoke in my bed, the moon was already out and nearly directly above. _"I can't believe it, everything I have here will be lost,"_ I was panicking, it felt my world was collapsing in on itself. _"I have to calm down somehow!"_ I was frantically searching my mind for something to grasp onto, a memory, story, anything at all. I recall when I found out that I was changing into a demon. I was never a brutal, ruthless killer until I was forced to become one.

Rem, the mentally broken Subaru, and I were going back to the mansion we lived in. I was forced to sit in the carriage as the broken Subaru got a lap pillow, in the front seat with Rem. When all of a sudden Rem had clutched her heart and leaned over, in seemingly pain. Her sudden heart attack was enough to send me into a state of both panic and alert. The poor ground dragon's head was then cut off, with a clean, magical cut. The carriage was then thrown over, knocking me out cold. I awoke to a fiery explosion going off around Rem, I forced myself up. There were Witch's cult members everywhere, it only took a split second for me to connect the dots. The Witch's cult had set up an ambush and we fell right into it.

Snapping back to reality I had to defend myself against all of the cultists running towards me. They were ruthless, and halfway through the battle Rem screamed something and ran away. They just kept coming at me, I was getting tired of trying to learn each member's specific attack preferences, and then counter them. I then slipped into a sort of pattern of: slice left, slice right, step back, slide forward, slice up, slice down, stab. I hated to admit it back then but I was having so much fun killing the Witch's cult, this was when I started getting the extreme headaches, right behind my forehead.

After I killed all of the Witch's cult that was attacking me, I immediately ran off at extreme speeds to where Rem was heading. I didn't know how I was going so fast, but I had more pressing issues. Hell, I didn't even know where I was going, I just felt that was where I needed to go. After one minute of running at high speeds, I came across a cave with the sound of clattering metal emanating away from it like how a wave emanates from the ocean. I instinctively knew to run in there and see who was fighting, I had a feeling that the Witch's cult had something to do with it.

When I arrived I was shocked at the sight of Rem dangling in the air by purple hands, I followed the purple hands and realized they were coming from a particularly ugly looking man. He noticed me immediately and launched yelled something about _"Unseen hand"_ and more purple hands shot out of his back. I recoiled in disgust as I was recovering from slicing the hands, he yelled even louder about his _"Unseen hand"_ and bent backwards. I saw the opportunity and immediately took it, I sprinted faster than I ever had prior to that moment. I sliced any cultists that were in my immediate path as I sprinted to the bent over man, when I reached him I cut into him. My relatively long knife went all the way from his pelvis up to his neck, where I pulled my blade out of his body. He immediately fell back and all of his _"Unseen hands"_ disappeared. I systematically killed all of the cultists in the cave.

After recovering from my combat trance I ran to Subaru, who was holding Rem and crying tears of joy. When I reached the two a sudden, sharp, pang hit me right behind my forehead, I collapsed. I was in extreme pain, despite not feeling anything. Rem had came to make sure that I was okay but Subaru didn't come to check on me, he just sat there. My senses were slowly dissipating first touch, then hearing, the smell of death disintegrated as I lost my sense of smell, I lost taste, and finally I delved into darkness.

I regained all of my senses at once in a jolt of energy and information. I shot open my eyes and looked around, Rem was surprised and was slowly getting off of me as I was sitting up. I looked towards Subaru who actually got up, he looked absolutely horrified, and surprised at the same time. I turned back to Rem who was discreetly pointing at my forehead as if she was trying to tell Subaru something and not me. I raised my hand to my forehead and hit something, sending chills down my spine and a somewhat intense pang throughout my head. Immediately realizing what was happening I thought of myself with a horn _"I don't look all that bad,"_ I had so innocently thought then. When I reentered reality after escaping my imagination I found that Rem was pretty much in my lap "Try to imagine yourself without a horn," Rem whispered into my right ear (I was never one to like ASMR but that whisper sent a weird feeling through me). Per her instructions I imagined myself without a horn on my head, and the slight dark red tint of the room (that I hadn't noticed) disappeared.

* * *

Exiting my mind I came to once more, calmed down now. I looked out the window and realized that at most I had a half an hour to be in this world, I picked up a pen and paper.

"Dear everyone,

It has come to my attention that I will no longer be able to be here anymore. I was brought here on accident and will be taken out of it. Please don't worry I am not dead, simply in another world restarting life, once more. I loved all of you, some more than others, however that does not matter anymore. Please tell anyone and everyone that I knew personally that I am no longer here and in a different world, I would hate anyone thinking that I was dead.

To Subaru, you know what I might be going through right now having to go to another world and all. Sorry for having to leave early, I would've loved to beat you in a sparring match once you got official training.

To Rem, you were probably the best person to help me through my transformation from only human to demi-human, I will forever remember you for teaching me how to utilize every ounce of strength that I have.

To Roswall, thank you for letting to strangers into your mansion. I know that I could probably never describe how thankful I am for you taking Subaru and I in.

To Ram, thanks for the laughs. In the darker days I had where I just didn't feel good, your witty insults and remarks toward me and Subaru helped brighten my dark days.

Thank you,

Sincerely, your best pal

Adrian "Razor" Scott"

* * *

With the letter written, I left it somewhere noticeable to anyone coming in. I ensured the door was unlocked, and laid down on my bed to wait.

Within the blink of an eye, my dimly lit ceiling changed to a dark, beautiful night. I started falling towards the ground with the slightest bit of panic but mostly calm. That's when I saw a giant black humanoid monster being lifted by thin golden wings from its waist, nearly right below me. After a few seconds of admiration it exploded into a ball of blue liquid, perhaps blood?

* * *

 **Edit: I accidentally got the time wrong, it was meant to be night instead of day. I changed that now so it really doesn't matter to anyone that are just now reading this.**

 **Thanks to anyone that favorited, followed, and/or reviewed**


	3. Testing

Chapter 2 – Testing

 **Okay, so quick side note. I'll be trying my best to pump these short chapters out every once or twice a week, maybe more if I feel like it. Also if enough people tell me to write longer chapters, I will do my best to follow their demands.**

 **Without further adieu Chapter 2 – Testing!**

" _Why the hell would it explode into BLUE?!"_ I screamed inside my head. I had bigger problems then that however. _"The blue glob is rapidly approaching and I don't have a way around it,"_ I was convincing myself to think of some way to avoid the glob. _"Perhaps I'll just go through it?"_ I was getting desperate with at most 50 meters and approaching fast, it was my best chance. "Through it is!" I yell out to affirm what I am thinking to myself.

Bringing my arms up to protect my face, I let myself plunge through the liquid. Going through the glob was like moving through water, that was also moving in the same direction you were heading.

 ***CLANG***

"Ow!" I hit something head on. I'm no longer moving? I open my eyes to see that I'm on some sort of giant white mech's shoulder. Upon further inspection I am on a sort of shoulder pad. The shoulder pad itself wasn't very easy to hold onto, seeing as it was probably made not too be held onto. Turning left it was staring into my soul, _"This is one of, if not the most awkward moment in my history..."_ I thought to myself. Observing the mech's head revealed very hard to miss details, the mech had seemingly golden ribbons of hair and a huge blue spike coming out of it's upper forehead. _"Could it be common? No,"_ I shut down my own hopes in favor of rationality. A boy's voice then spoke, I couldn't make out what it said but I could tell it wasn't directed to me. The voice came from somewhere within the upper body of the mech. Even with my heightened senses due to not being exactly human didn't allow me to pick up the words.

It seems as though the boy's voice was speaking to a woman. The woman seemed to be demanding or ordering the poor boy around. Realizing that I was safe for a second, I took a chance to observe the entire mech. From head to toe the mech's main color was pure white, with red thrown in to compliment the white body. The body of the mech was VERY feminine with what seemed like a skirt and everything. At this point the ball of blue liquid had long since fallen to the ground and I was able to get a sense of how high we were. Looking over the shoulder it was apparent that the only way we were still in the air was by the fiery exhaust coming from the back of the skirt. _"It must be more than a sort of skirt then, right?"_ I questioned my previous logic from my observation of the front. Glancing back to the face of the mech, it was still most definitely watching me with either curiosity or impatience.

Observing the ground once more under the moonlight it wasn't hard to miss two giant semi-spheres attached by a tunnel with a metric-fuck-ton of lights all over it. Adorning the semi-spheres was I giant glass top with trees inside, it kind of looked like a birdcage but for people. There were even more mechs dotting the ground, probably more than nine in total. Four of which were completely unique to all the others, being differently colored than the more uniform and grey-scale five or so.

We started descending at a very rapid rate, me making sure to hold on as best as I could to the shoulder or any handle I could grab. As we fell the giant mech spoke it's first words to me, "Who are you? Where are you from?"

"'Scuse me, I don't think now is the perfect time to have small talk!" I had to yell over the sound of the wind passing my ears.

"If you don't tell us, we will have to run tests on you immediately," this time the actual mouth of the mech moved, and the voice was unmistakably feminine.

I sighed and started yelling, "Well, I'm not from round here, and I'm Adrian or you can call me Razor!"

"What is your code?"

"Code?" I was panicking at this point, we were getting close to the ground and I didn't want to reveal my little secret to this world yet. The second part of my worries was that I didn't have a code, and didn't know how to respond. _"Here goes nothing,"_ I reassuringly thought to myself. "I, uh, don't have a code. I told you that I'm not from around here!" I put my secret into this singular line. The mech seemed taken back and I could tell that it was thinking of what to do with me.

Silence, as we fell through the sky. All of a sudden I felt uncommonly heavy so I opened my eyes. The mech's skirt thrusters were firing at seemingly full throttle, looking back to it's face, it was looking down as if it were checking how low we were. Once on the ground it grabbed me with it's right hand. I squirmed as much as any person could while being held in a death grip of a giant mech. Considering all of the possible consequences that could come from me misbehaving, I decided to play by the rules for now.

After about 10 minutes the mech had regrouped with one other mech that seemed to be in charge. The other mech was similar to the one that's holding me, instead of red highlights they were blue. "What are we going to do with it, Ichigo?" The male voice was coming from the red mech this time in a hushed whisper.

"Nana said we need to take it in for questioning and tests, we can't kill it." The mechs were conversing about what to do with something, presumably me.

Now I was starting to get restless, "When am I going to be able to walk freely?" I questioned the two, hoping to get a good answer. All I got was a blank stare from the one in charge, or Ichigo I think they called it. I immediately got the message and shut up. "Soon enough," the red mech had actually replied to my question, Ichigo was clearly irritated by the red's answer. The two seemed to be trying to hide that they were going to test me, clearly they didn't know I overheard them deciding my possible fate.

Again we were off, this time heading to the two giant semi-circles with the Ichigo. The closer we got to the semi-circles the more mechs that joined us, in the order they joined us in there was a pink mech, then black, and finally a purple mech. It seemed as though the team was trying their (very literal) best to stay in formation, as if they were used to being slightly more casual.

Once we reached the giant semi-circles we went to the one on the right, it was giant and white, it had a huge dimly lit orange spot on it that had lines leading out of it in three different locations. The lines were probably power lines, making the orange spot either some sort of huge battery or generator. Under the huge semi-circle was a shaded region of darker gray and huge doors for the mechs. At the huge doors was where we currently were, waiting for something. "Can I walk, now?" I shot the question out there for anyone to answer, somewhat expecting no one to answer from how they've been so silent. Ichigo nodded to the mech that was holding me, and I was brought down to the ground. Only now did I truly get a scale on how large the mechs really were just on rough estimates they were at least 40 meters tall (131.234 ft for my fellow imperialists).

A normal sized door opened and out flooded soldiers heavily armed and in protective gear with masks on. The lasers of their rifles were all on me, one on my forehead, chest, pelvis, right foot, both my knees, and my neck. None of them were moving. "Hello?" I tried my very best to break the kilometer thick ice, but to no avail.

"Hands behind your head!" One of them barked at me, I had absolutely no choice but to follow their orders.

"Now on the ground!" Again I followed the orders they gave me, I could feel the lasers and stares of the mechs on my back. One rushed to me and grabbed my hands from my head to behind my back and put some sort of handcuffs on. Then I was hoisted up by the handcuffs and I was ushered into the door.

 **Now we're getting somewhere, eh? Sorry for not posting until now, I literally only wrote three sentences on Thursday, oops. Next chapter will, if all goes right, be up by Friday**

 **Many thanks to everyone that**

 **favorited, followed, and/or reviewed .**


	4. Induction

**Welp... Heh, I've really fucked up. School required two huge projects, and I thought I could get everything done early. Boy was I wrong. Anyway, I know all of you have been waiting for this chapter, as I left it on a cliffhanger last time.**

 **Also I'll be changing thoughts from** _ **"This"**_ **to** _ **'This.'**_ **A simple change but I hope it makes thoughts and dialogue easier to separate.**

 **Without further adieu Chapter 3 – Induction**

* * *

I was forced into the bright white hallway by the guards, who probably underestimated me. It makes perfect sense that they'd underestimate my abilities, after all I look like a scrawny, tall 17 year old who lived in his mother's basement for half his life. All of a sudden I was hit in the back of the neck with something very powerful, by someone immensely strong. I felt light and weak, I couldn't move and my eyelids slowly shut as they dragged me through another door.

I awoke in a brightly lit, white room with very little to describe; there was a single bed, a toilet, a sink, and a shut door. The only different color in the whole room was a single line of orange at eye level going entirely around the room. ' _Am I in a holding cell?'_ I questioned myself, hoping that I could get out. Looking down at myself my clothes had been ruffled around. ' _Did they search me!?'_ I frantically patted myself down, checking for my possessions . Though my possessions were seemingly meaningless they meant the world to me, I had a rock that I collected at the site where I became a demon. Though some wouldn't want to remember these moments, as they could interpret that that's the moment they lost their humanity. To me however, this meant more of an opening of a door to a world of new possibilities. My one other possession I had on me was a preserved flower from the fields where we defeated the White Whale, no need to go into detail. The last possession I had was a simple Ipod with all my favorite music on it, it had died but I was able to resurrect it with magic. All of which were completely missing.

I checked my body underneath and observed a bunch of small bandages and tiny pinpricks where needles had probably poked me. Upon looking at my arms once more, even more of the pin pricks made themselves know to me.

An unfamiliar sound was behind me to my right, right where the door is. Whipping around I was ready for a fight, instead a woman was standing there. She had light brown hair that went down to her shoulders, and she was wearing a gray long sleeve shirt. She was wearing some sort of long dress shorts, that went from right below her * **cough** * jugulars all the way down to her ankles with one leg sticking out from a weird design choice. She seemed to be an adult and in charge, hoping to get answers I exited my overly-defensive stance. "You have a code now, you will be referred to by your code and only your code. Your code is 001," She told me, it seems as if she's put on a mask of courage when she was really actually nervous.

"Ok, but when will I get out of here?" I decided to probe to see how much information I can dig out.

"You will leave once we test your ability to be a parasite," With that she left the room and another whir of the door.

* * *

The past three days, no weeks? I can't really tell, had been painfully boring with nothing happening except me in this room thinking about songs. Daily rations were the highlights of my days in the room, if nothing is happening then food becomes the highlight of everyday.

Like the first time the door had opened I twisted around, and was pleasantly surprised, to see that the light brown haired woman had returned. "It's time for your testing," She announced to me.

"Is anyone going to hit me over the head this time? That was my favorite part about when I was brought here," it felt like I put so much irony in that last sentence that she was taken back from it.

She quickly recovered however, and told me a simple, "No, follow me." Without a word I got up and followed her through the door and out into the bright white corridor. Thoughts began to flood into my head as I switched into autopilot and followed her. ' _What do they mean by testing?!'_ _'What are they going to do? Will they just give me a standardized test?'_ Hoping for a standardized test I took a deep breath as we stopped moving. "We're here," she said dully. "Beyond this door are pistills that are willing to test you and themselves, if all goes well we will learn about your abilities," She was as dead as ever.

"How are you going to test my ability to be their partner?" I asked the woman, with a small, demented side of me hoping it would be something sexual.

"You and one of the pistils will enter the pod in the center,and when the grips come out, grab them," She ordered, then she opened then the door. Looking at their outfits, it was clear I was out of place. I was wearing black and red shoes, somewhat black jeans, a plain black shirt, and on top of that a light and dark blue striped jacket. Meanwhile they were all wearing skin tight suits with what seemed like a mechanical hood on the back. The woman with light brown hair moved over to where the pistills had gathered, I on the other hand migrated my way to the pod and started to learn it's intricacies. The pod was nothing fabulous, it had a basic, slick design and looked like an untextured or shaderless object in a video game. It had two parts to it, the top was a completely different color altogether. The top was a very slick looking black, and the bottom half was a light gray with very little to it. To both the right and left of the pod were monitors, wires, and what I assumed are some sort of machines to monitor what was occurring within the pod.

Just then something tapped my shoulder, suppressing my urge to react at light speed I (relatively) slowly turned around, one of the girls was there. Her face was slightly more human than the woman that brought me here, analyzing her facial features was easy, as nothing stood out. her eyes were a beautiful bright shade of blue, and her hair was black with a few white hairs appearing every now and again. "It's time for us to test our compatibility," she cheerfully exclaimed to me, it was crystal clear that she was excited to test with me or perhaps she was just told to act this way. Either way I gave her a little nod to say that I was ready. She turned around "We're ready!" she enthusiastically informed the woman.

* * *

It was two hours after the testing finished, nothing important really happened but I can say that the awkwardness and sexuality of the position was not lost on me at all, I had to sit in a seat then the pistill laid on their stomachs in front of me with their rear-ends just a few mere centimeters away. As expected the little grips popped out from their holsters, that were on the pistills rear-ends. Needless to say, I was shocked but I followed along anyway.

Everything was smooth up until I had exhausted all the pistills and realized that I was incompatible with everyone, trying to give them a reason to keep me alive I offered that I try to sit in the pod alone in the pistill's position. That one time that I tried the pistill spot it felt like I was one with the pod, I even heard (what I assumed) the monitoring machines spin up and aggressively whir and hum, as if they were receiving too much information or power. After I got out there were more soldiers there and immediately I was shocked with a taser and knocked out.

That brings me to now, sitting in a smaller cell with two of the military dudes clad in black watching me. The only real difference was that it felt like I was on a plane.

* * *

 **Sorry so, so, so much I just haven't had the motivation to do this. I will try my very best to get this out more often**

 **Many thanks to anyone the followed, favorited, or reviewed**


	5. Woops, sorry

**Ok, I found a major issue that had occurred somewhere in my story and I kind of accidentally did something not good. I've fixed it now and hopefully whoever reads this will check the first chapter to see that it has changed!**

 **I had a major issue where all of my (3) chapters moved down so they were a bit broken but that's fixed now!**

 **Sorry for the spam!**


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